A model today spoke of the “pressure” to stay slim and claimed that her agency had advised her that she needs to lose weight if she wants to stay in the industry.

Lilah Parsons, who has worked for Vivienne Westwood and Chanel, gave up modelling full-time after she got a job as a presenter on MTV.

Now Parsons, 25, claims she has been told by agency Models 1 that if she wants to do more modelling she needs to lose weight, after going up “a size or two”.

She said she “loves” food and does not believe in “irresponsible” dieting — but has put herself on a five-day juice regime, joined the gym and got a personal trainer because she wants to continue modelling.

Parsons, who is the daughter of the Queen’s former deputy keeper of the privy purse, said: “I have been concentrating on my TV career recently and it’s great, there is less pressure on a TV presenter to be a certain size so I probably haven’t watched what I have eaten so much.

“And when you’re on set you’re grabbing something quick and easy to eat, which isn’t always the healthy option.

“So it’s fair to say that I have gone up a size or two since I was modelling full time. And unfortunately size 12s don’t fit in the designer’s sample sizes. And because I want to carry on modelling, this is something I have been told to consider.

“Over the years I have seen many young girls diet irresponsibly as they believe that’s the way to make it as a model. It’s very sad to see but there is so much pressure.”

Parsons started modelling after she was spotted at a party in east London when she was 20. Six weeks later she was shooting for Chanel and doing catwalk shows for Westwood.

However, after four years of modelling full time, she decided to start going for screen tests after she realised she preferred working with film crews over photographers.

Parsons, who is presenting from the Wireless festival at the Olympic Park next week, said models should balance healthy eating and exercise rather than dieting. She said: “I think young aspiring models need to remember that there are ways of maintaining a good and healthy figure the right way. Exercise and healthy eating.”

Max Clifford Associates, which represents Parsons in her TV work, confirmed that she had been asked to lose weight by her modelling agency.